Author: martin fierz
Date: 20:30:40 07/16/02
Go up one level in this thread
On July 16, 2002 at 20:31:49, Robert Hyatt wrote: >On July 16, 2002 at 18:39:53, Gerd Isenberg wrote: > >>On July 16, 2002 at 18:25:08, Robert Hyatt wrote: >> >>>On July 16, 2002 at 18:10:59, Uri Blass wrote: >>> >>>>On July 16, 2002 at 17:44:36, Robert Hyatt wrote: >>>> >>>>>On July 16, 2002 at 17:38:02, Uri Blass wrote: >>>>> >>>>>>On July 16, 2002 at 16:52:33, Robert Hyatt wrote: >>>>>> >>>>>>>On July 16, 2002 at 14:32:57, Russell Reagan wrote: >>>>>>> >>>>>>>>On July 16, 2002 at 11:07:10, Robert Hyatt wrote: >>>>>>>> >>>>>>>>>However, with _no_ book you leave yourself open for preparation of traps. I >>>>>>>>>saw Ken Thompson do this to NuChess years ago at an ACM event. You don't want >>>>>>>>>to leave that kind of "hole" for a major event... >>>>>>>> >>>>>>>>Was it a trap set specifically for that engine? Or was it just a general trap >>>>>>>>that many engines fall for when left on their own? >>>>>>>> >>>>>>>>Russell >>>>>>> >>>>>>> >>>>>>>Sort of both. >>>>>>> >>>>>>>1. Ken knew which opening Nuchess would play, as ken was white and they >>>>>>>had a pretty narrow book. He simply added a line that made them go out of >>>>>>>book pretty early, with a classic trap where they gave up a piece to win >>>>>>>the rook at a1, and thought they were winning an exchange and losing a pawn. >>>>>>>In reality, they lost both pieces plus the pawn, and the game. >>>>>> >>>>>>It is not going to work against Movei even in bullet. >>>>>> >>>>>>Movei evaluates black knight at a1 as clearly less than a knight in normal >>>>>>squares and the difference in evaluation is slightly more than a pawn. >>>>> >>>>>Look out on ICC. Would you rather lose a pawn or be forced to place your >>>>>knight on A1/H1 for a while? I would prefer to stick the knight on the >>>>>corner, because that can be corrected later. Losing the pawn is losing the >>>>>pawn, period. You can't make it come back later. >>>> >>>>There are often cases when the black knight cannot come out of a1 later. >>>> >>>>I prefer to lose a pawn for a probability of 40% to win the knight and I suspect >>>>that it is more than 40%. >>>> >>>>If the knight is not trapped there is a good chance that the search can get it >>>>out of the corner and it is easier relative to the case that the knight is >>>>trapped because if it is trapped you may need many moves to capture it and in >>>>most of the cases when it is not trapped you can get it out of the corner in one >>>>move. >>>> >>>>I also saw games when Movei beated other programs because the knight of the >>>>opponent was trapped in the corner. >>>> >>>>I think that these cases are more common then the cases when Movei is losing >>>>games because it evaluates the corner too much. >>>> >>>>Uri >>> >>> >>>I used to have a much larger corner penalty. And found on a few occasions >>>that playing Nh1 to defend the pawn on f2 was the right move. But the program >>>refused to do so because it thought that having the knight on H1 was worse than >>>losing the pawn on f2. It was unfortunately mistaken. :) >>> >>>Big positional scores are perfectly OK. But you had better be sure that they >>>don't have outlandish side-effects. This one sounds like it will... at a time >>>when you least expect it. >> >>Did you mean a white knight on H1? >>May be the corner penalty makes more sence with white pawns on A8 or H8 only, >>where they are likely to get trapped. > >I thought Uri said "corner squares". Which is more dangerous than "corner >squares on the enemy side of the board". But even then there are probably ways >to exploit a program that thinks a knight on a8 is really bad... like when it's good to go and grab the exchange the program won't do it... sounds to me like not evaluating it and evaluating a knight in the corner as -1 pawn are both quite wrong - a bit more knowledge should be able to do much better than that! aloha martin
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